DIPHTHERIA BACILLUS . 83 



washed in water and Bismarck brown applied for i or 2 minutes, the bars 

 and granules appear deep blue, intervening portions light brown. The diph- 

 theria bacillus is Gram positive. It is not motile. 



There are so many variations in the morphology of true diphtheria bacilli 

 and so many similar pseudodiphtheria and non-pathogenic bacilli that it is 

 important to know them. For this reason and to assist in the differentiation 

 between pathogenic and non-pathogenic forms Westbrook has described a 

 classification which has been accepted by many health department laboratories 

 and bacteriologists. It may be summarized as follows: 



Type A. Decanter or Indian-club shaped, showing one, i /* to 2 /* thick 

 two or more round granules, arranged together, or more fre- 3 ^ to 6 n long 

 quently distributed; situated at one or both poles, or through- 

 out the length of the organism. 



Type A 1 . Same shape and size as A but presenting bars in place of granules. 



Type A 2 . Same size and shape, solid uniform staining. 



Type B. Long slim straight or curved rods, one, two or 0.5 /z thick 

 more round granules arranged together, or more frequently 3 p. to 7 n long 

 distributed; situated at one or both poles or throughout the 

 length of the organism. 



Type B 1 .- Same size and shape as B but presenting bars in pla~ of granules. 



Type B 2 . Same size and shape, solid uniform staining. 



Type C. Straight or curved rods, frequently slightly 0.5 ju to i.o ^ thick 

 swollen at one or both ends, one or two round polar gran- 3 ^ to 6 /x long 

 ules, and occasionally a third granule near the middle. 



Type C 1 . Same size and shape as C but presenting bars in place of granules, 

 five or more bars may be observed. 



Type C 2 . Same size and shape, uniform staining. 



Type D. Straight or curved rods, two round gran- 0.75 JJL to i.oo ju thick 

 ules situated one at each pole. 2ju to 3 p long 



Type D 1 . Straight or slightly curved rod and carrot- 0.5 y. to i.o M thick 

 shaped, showing two, three, four or occasionally more 2 ju to 3 yu long 

 bars. 



Type D 2 . Isosceles triangle-shaped, usually in pairs 0.75 ju to i.oo ju thick 

 with bases in apposition solid and uniform staining. i.o /-i to 2.5 n long 



Type E. Straight or curved rods and ovoids, two 0.50 ju to 0.75 JJL thick 

 round granules situated one at each end. i n to 2 ju long 



Type E 1 . Same size and shape as E but presenting two, three or four bars 

 in place of granules. 



Type E 2 . Same size, blunt cone-shaped, usually in pairs with bases in appo- 

 sition solid and uniform staining. 



Type F. Straight rods, one round polar granule and 0.25 ^ to 0.50 /z thick 

 occasionally a central granule. i /* to 2 '/* long 



Type F 2 . Same size, irregular rod-shaped, solid uniform staining. 



Type G. Ovoids, two small round granules situ- 0.50 /x to 0.75 ju thick 

 ated one at each pole. i.o ju to 1.5 /* long 



